Dual extrusion how-to

[foshon]

Ok a few have asked so here is my:

The Officially Unofficial Guide to Dual Extruding the Max


I'll skip the basics and assume that you have the following:

1. Two hotends with level nozzle height mounted to the effector.
2. These hotends are identical in every way.
3. Two extruder assemblies with identical settings (motor, drive gear)
4. Complete wiring for both heaters, thermistors, and extruders.
5. The RamBo electronics V1.1 that are currently shipping with the MAX.
6. You have Repetier firmware installed on the electronics and the EEProm is enabled.
7. You control your MAX using Repetier host.



Alright the firmware changes first.

Edit this by changing the digit after NUM_EXTRUDER from “1” to “2”:


// ##########################################################################################
// ## Extruder configuration ##
// ##########################################################################################

/** Number of extruders. Maximum 2 extruder. */
#define NUM_EXTRUDER 1


Now you will want to edit the settings for EXT1 to match the settings for EXT0. Once again assuming extrusion set number two is equal in every way to set number one make all of these identical as well. The really important bits are:

#define EXT0_STEPS_PER_MM
#define EXT0_TEMPSENSOR_TYPE
#define EXT0_MAX_FEEDRATE
#define EXT0_MAX_ACCELERATION
#define EXT0_PID_INTEGRAL_DRIVE_MAX
#define EXT0_PID_INTEGRAL_DRIVE_MIN
#define EXT0_PID_P
#define EXT0_PID_I
#define EXT0_PID_D
#define EXT0_PID_MAX

Now down near the bottom of the configuration.h you will want to change the zero in the MOTOR_CURRENT define to match what the number directly preceding it is set to. It is also wise to check and make sure your microstepping is set to 16 for the new extruder as well, again the last digit but in the MICROSTEP_MODES define.

NOTE: If you have an earlier version of the electronics these will be 8's not 16's, don't fret just make sure its the same.

Ok I think that covers firmware, now verify it, save it, and upload it to the board.


Now open up Repetier host but do not connect yet. Select “Config” from the top bar menu, then “Printer Settings”, now select the “Printer” tab. There is a selection for number of extruders select 2 and apply.

I recommend closing the program and reopening with the new settings, probably don't have to but I'm anal like that. Open it up again, and connect.

Recalibrate your z-height and individual tower heights just like normal, pay attention to how well aligned the nozzles are to the build platform. If one nozzle is higher than the other I would recommend fixing it now or your layer height between nozzles will never be the same. This is also a good time to select each one and ensure that it heats and extrudes properly.

Now you need to find your extruder offset. This will vary greatly depending on how you installed your nozzles. I will explain how I did mine.

1. Cover the bed in painters tape, or anything markable.
2. Clean of the nozzle tips of any plastic left hanging
3. Find and mark as accurately as possible the center of your bed.
4. Drop the nozzles to z0 (carefully).
5. Heat the nozzles up.
6. Let it sit a couple of seconds at temp and home the machine.

If you had plastic in your nozzles this will leave two tiny little dots of plastic exactly where they impact the bed opposed to XY zero at Z zero. Measure the distance of both from the center of the bed, note the direction the tiny dot is from zero. Doing it this way gives you a definite measurement of real life locations and worked far better, for me, then trying to measure off the effector.

Now open up the EEProm and scroll down to EXT0 X_OFFSET and its companion for the Y axis. Calculate how many steps will have to take to with each axis to get to the mark at zero. You will need to not the direction to zero as well, if the axis has to move in the negative direction then you want a negative number of steps. If both dots are off of your center mark then you will need change the EXT1 offset settings as well. When all the changes have been made close the EEProm and disconnect Repetier host.

Now reconnect the host, home the machine and run the head back down to z0. In the manual control section of the host select extruder 1. The machine will move extruder one where you told it zero was. If it is zero, hooray! If not, make sure your steps/mm and direction of travel are correct. Select extruder two and verify it's position as well. It took me a couple of tries to get this perfect.

I'm sure I'll be editing later, let me know what I screwed up please.

[foshon]

Really?! no comments at all? Feedback is a good thing.

[JohnStack]

Really?! no comments at all? Feedback is a good thing.

LOL, I'm just seeing this - of course I'm PST...everyone else must be doing things with their families...

Anyway, not having dual extruders but wanting them - I totally get this.

The question I have is about measuring. You're just measuring the absolute distance from the Extruder 0 tip to the Extruder 1 tip? or are you measuring both X and Y.

This might be in left field since I don't have one:
I'm wondering if there wouldn't be a way to measure offset prior to final assembly and then do homing, etc. The Z-orientation is usually always 0.

Also, I have asked SeeMeCNC to add sighting lines on the heated bed. In this regard, I believe they would help.

Photos?

NICE WORK and THANKS!

[jesse]

What about the software side? How does slicing work?

[JohnStack]

What about the software side? How does slicing work?

Thanks @Jesse - definitely...

[foshon]

Really?! no comments at all? Feedback is a good thing.

LOL, I'm just seeing this - of course I'm PST...everyone else must be doing things with their families...

Anyway, not having dual extruders but wanting them - I totally get this.

The question I have is about measuring. You're just measuring the absolute distance from the Extruder 0 tip to the Extruder 1 tip? or are you measuring both X and Y.

This might be in left field since I don't have one:
I'm wondering if there wouldn't be a way to measure offset prior to final assembly and then do homing, etc. The Z-orientation is usually always 0.

Also, I have asked SeeMeCNC to add sighting lines on the heated bed. In this regard, I believe they would help.

Photos?

NICE WORK and THANKS!

The distance between the two nozzles matters more for folks that have one nozzle at the zero position. On the MAX, it would be impossible to have one at the perfect zero position and then just use the distance between them as an offset. I recommend calculating it the way I do because it is very difficult to mount the nozzle in a perfect orientation to either the X or Y travel directions.

[Eaglezsoar]

Good writeup Neal. Jesse asked about the software side of things and without writing a book, could you give us a brief rundown on what you would have to do at the slicer level
to make use of the dual extruders. Did you use two of the Seemecnc or the E3D hotends? Can we see some pictures, I am interested in seeing how you handled the fans for the
extruders. You make a lot of good posts and this one is one of your best. Sorry for so many questions.

[Flateric]

I found one excellent way to align the two hotends when I was setting up mine was to print the thin walled calibration cube with one hotend and cancel it as soon as the first layer of the perimeter is complete and has good adhesion on the glass.

Now print the exact same print again but only with the second hotend and again cancel as soon as the first layer is printed.

Move the effector up and out of the way and then grab your calipers and measure the offests between the two squares to get your x and y vales.

Plug these in and redo.

Both of the first layers should print down exactly in the same location on the print bed.

Multiple tries are required to get it "just right" of course.

But for me this worked really well.

[foshon]

@Jesse/Carl: I only used slicer for testing. In slicer you also have to designate dual extruders, under the printer tab I believe. There is an area to enter the offsets for the nozzles in Slic3rs that you will not use because you made changes to your firmware. If you want to make one g-code file for your multicolor print (Slic3r allows for selection for support, perimeters, or infill) you have to have two STL's to combine. Also you must have the full version of Slic3r open to do it. Check Slic3r documentation for further instructions there, it's convoluted and an overall crappy way to do it (much better then the slicing software I wrote though ) The software side of things is the number one reason I had no issues taking my dual setup offline (cheap extruders). There is no simple way to design and print a one file multiple color object. All the methods I have seen involve cutting up g-code.

@Flateric: That's a good idea. I went the dot route because it seemed easier to find the relative position of 3 dots, center of bed, and the nozzles.

[jesse]

I wonder how difficult it would be to change color every other layer

[Generic Default]

I just got an E3D and a cold end setup so I can do dual extruders with the stock hotend and the E3D.

I did all of the changes to the firmware in this thread as well as the newer thread on dual extruders that explains what to change in the pins.h file.
When I switch between extruder 1 and extruder 2 in the repetier host manual control window, the LCD panel beeps rapidly for a tenth of a second or so. I can't extrude or retract either extruder, and the none of the heater cartridges work. The red LEDS on the rambo don't light up. What's wrong? Is there anything else I'm missing?

I did change the EEPROM for the second extruder.

EDIT:

After a little bit of troubleshooting, I narrowed it down to #define NUM_EXTRUDER

If I set it at 1, the extruder works fine and reacts to commands for both extruder 1 and extruder 2 in repetier host.
If I set it to 2, nothing works at all.



I still haven't figured it out. Is anybody else having problems setting 2 extruders in the firmware?

[foshon]

what happens if you swap all components from 2 to 1 (heater,therm,motor)?

[Generic Default]

Problem solved! (I think)

After switching all of the E2 components (heater, thermistor, motor) to the E1 plug slots, I saw that all of them worked except the thermistor. After a bunch of failed continuity testing I narrowed it down to a white wire. It turns out that all of my problems were caused by a discontinuous thermistor crimp. I bought a ribbon of 40 crimped single female pin wires from amazon and some of them are defective.

Now that I can control both motors and both thermistors it seems to be working fine. It looks like dual extruders are going to work for me! FINALLY!



This might be ambitious, but the rambo board has 6 stepper motor outputs. The rostock uses 3 for movement, one for the extruder, a second for a dual extruder extension, and one extra for a 2nd Z axis stepper for mendel printers that need 2 z axis motors.

Thank you to everyone who helped me out here.

Could we possibly plug a 3rd extruder into that one to use for a triple extruder system? We would have to modify the firmware and pin setup, but other than firmware would anything prevent us from doing this?

[Generic Default]

I still don't have dual extrusion working, this time because of alignment and calibration problems. My delta platform rotates just a tiny bit when it moves around the build area, and this rotation, even though it's too small to see, is causing the nozzles to get offset from each other as they move around the glass bed. At one end of the bed, the one nozzle is lower than the other. At the other end, they switched and the lower one is now too high. It's a difference of about 1mm over the build area, but that's way too much for printing. I checked to make sure the towers are parallel, and they are, and I checked the arms to make sure they're the same length, and they are.

I've made a few different effector platforms and I rendered my last two iterations. My newest one has both the seemecnc hotend and an E3D hotend on magnetic ball joints. The E3D one is set up with an adapter to input filament from up to three different extruders (not at the same time; it's meant for dual extrusion with retraction, not color mixing).

The adapter that merges the filaments into the hotend works great, but my cold end extruders really suck. Both my steve's extruder and greg's extruder constantly jam and grind and can't do decent retracts. They were just as bad before I had this design but the design won't work decently until get my extruders working right. I need to figure out how to prevent my effector platform from rotating while moving. When I eventually build my own printer, I'll probably go with a cartesian one to avoid all of these geometry complications.

[Michi86]

Hey Generic Default,
could you please upload the stl file for the mounting that would be outstanding
Thanks in advance!

[Generic Default]

Here you go. It's a set of a few stls, so just print them all at once or something. I made mine out of trimmer line nylon with 3mm shells and 30% fill in Cura.

You need some screws around 3 or 4 mm x 20mm

[kbob]

Nice design! May I ask what modeler you used?

Are the honeycomb holes for cooling, weight reduction, or just because they look good?

As for your platform rotation, I wonder if your ball joints are not all at the same height. If one arm of a pair had a smaller vertical drop than its twin, then it would move further in the horizontal plane.

You can check the effector platform by setting it upside down on a flat surface. Check that all six balls contact the surface. I'm not sure what the best way to measure the height of the balls on the carriage. Maybe set a precisely planed brick on the bed and bring the balls down until they touch it.

And then, if that finds the error, you'll have to figure out how to correct it.

[Generic Default]

I use Solidworks. It's excellent for this kind of stuff, and you can get the full version absolutely free from certain websites...

The hex holes are mostly for routing the wiring through and maybe future attachments like cooling fans and stuff. They're also a lot more rigid than the straight line infill that cura puts in at 30%.

I'll check the effector plate balls to make sure they're level, but this kind of stuff is a lot harder than it looks to fix! I know exactly what the problem is, but I don't know what's causing it.

The method I used on this design to get the two different types of nozzles level works really well. There is a printable nylon spacer nut between the threads and the groove of the seemecnc hotend, and you just tighten the steel nut on top of it to compress the nylon nut a few hundredths of a millimeter to get it perfectly aligned with the E3d nozzle. All of that precision is useless when the whole thing tilts though, so make sure your delta platform is perfect.

[pyrophreek]

I have been following your instructions, as well as loading the firmware supplied in an earlier post, but having no luck with getting the second extruder to work properly. Every time I tell it to extrude, it starts rotating back and forth. I have checked the wiring, and it works when I swap it with my original extruder, so it is not the motor or wiring. What would cause this?

[dpmacri]

I have been following your instructions, as well as loading the firmware supplied in an earlier post, but having no luck with getting the second extruder to work properly. Every time I tell it to extrude, it starts rotating back and forth. I have checked the wiring, and it works when I swap it with my original extruder, so it is not the motor or wiring. What would cause this?

I started seeing something a little like this after setting up dual extruders. Basically, the stepper drivers start overheating causing shutdowns/skips. I pointed an 80mm, 12v fan at the slot where the USB cord goes into the RMAX so that air would blow over the back of the RAMBo. That seemed to fix the problem for me (assuming your problem is the same).

I have this feeling that perhaps I had to do something else to get the 2nd extruder to work initially (I recall doing the same kind of testing you've described). But I can't remember what that was Which firmware version are you using? I was on Repetier 0.83.

[pyrophreek]

Rep 0.8 Maybe I need to try the latest.

[pyrophreek]

Any chance I could get a copy of your firmware? Would be nice to start with something I know should work for dual extruders.

[dpmacri]

I modified the .83 firmware that SeeMeCnc has in the github RostockMAX repository here: https://github.com/seemecnc/RostockMAX. I only needed to modify Configuration.h and Pins.h. I'm attaching both. One thing I just remember when looking through the changes I made is that the default current for the 2nd extruder is 0. I set mine to 225 which is the last number in this line:

#define MOTOR_CURRENT {195,195,195,225,225}

I think that may have been the piece I missed initially.

My hot-ends are dual E3D using the RP-One Labs thermistors (http://www.ebay.com/itm/Modular-Screw-o ... 33873faca2)

They're spaced 25.0mm apart which is why the distances are -1000 and +1000 (Steps/mm = 80, 12.5 mm in each direction).

Configuration.h

Configuration.h for dual extruders

(47.71 KiB) Downloaded 546 times

Configuration.h

Configuration.h for dual extruders

(47.71 KiB) Downloaded 546 times

[pyrophreek]

Thank you, apprreciate it.
Got it installed, and it seems to work alright for everything else, but the motor still does strange things. When I tell it to extrude, it begins spinning backwards and wont stop even if I hit emergency stop. Only way to shut it off is to turn off the power.

[pyrophreek]

Figured it out....The settings in the EEPROM were bad...lol so easy